PHOENIX -- A gunman opened fire at office complex in Arizona's largest city Wednesday, killing the CEO of a company, wounding two other people and setting off a manhunt. Police warned the public that the suspect was "armed and dangerous."

Authorities identified the suspect as Arthur D. Harmon, who they said opened fire at the end of a mediation session. Authorities believe Harmon acted alone and fled the scene in a car after the 10:30 a.m. shooting. Sgt. Tommy Thompson, a Phoenix police spokesman.

Harmon allegedly shot at someone who tried to follow him after the shooting in an attempt to get his license plate number, according to authorities.

Authorities identified a man who died hours after the shooting as 48-year-old Steve Singer. Police believe he was the target of the attack, along with a 43-year-old man who was wounded, Thompson said.

"It was not a random shooting," Thompson said.

According to court documents, Harmon had filed a lawsuit against Scottsdale-based Fusion Contact Centers LLC, where Singer was the CEO.

America's latest public shooting came on the same day Congress took up the issue of gun control for the first time since the Connecticut school shooting in December left 20 young children dead and changed the national conversation on guns.

Former Arizona Rep. Gabrielle Giffords, who was shot in the head during a 2011 shooting rampage in Tucson that left 6 people dead, appeared in Washington to testify in favour of stricter gun controls.

As police searched for the suspect in Wednesday's shooting, SWAT teams and two armoured vehicles surrounded a home about 7 miles (11 kilometres) from the shooting scene. Police served a search warrant to enter the home, which county property records show was sold by Harmon to his son last year for $26,000.

For a time, officers, believing the shooter might be inside, used a megaphone to ask him to surrender.

The gunfire at the office complex prompted terrified workers to lock the doors to their offices and hide far from the windows. SWAT officers searched the building.

"Everyone was just scared, honestly, just scared," said Navika Sood, assistant director of nursing at First at Home Health Services who along with her co-workers locked the entrances to their office.

Sood said police evacuated the office about 30 minutes after she first heard the popping noises.

Police didn't immediately release the names of the wounded. But a Phoenix law firm, Osborn Maledon, said one of its lawyers, Mark Hummels, was among the wounded. The firm said he "was representing a client in a mediation" when he was shot.

According to court documents, Harmon was scheduled to go to a law office in the same building where the shooting took place for a settlement conference in lawsuit he filed last April against Fusion. Hummels was representing Fusion in the lawsuit.

The company had hired Harmon to refurbish office cubicles at two call centres in California, but a contract dispute arose.

Fusion said Harmon was paid nearly $30,000 under the $47,000 contract but asked him to repay much of the money when the company discovered that the cubicles could not be refurbished, according to the documents.

Harmon argued Fusion hung him out to dry by telling him to remove and store 206 "worthless" work stations after the mix-up was discovered. Harmon said Fusion then told him that the company decided to use a competitor.

Harmon's lawsuit had sought payment for the remainder of the contract, $20,000 in damages and reimbursement for storage fees and legal costs.

Pro tempore Judge Ira Schwartz, who scheduled the meeting, did not immediately return an email seeking comment. A message left Wednesday at Singer's home also was not returned.

Vanessa Brogan, who works in sales support at an insurance business in the three-story complex, said she heard a loud bang that she thought at first was from somebody working in or near the building.

She said others at the business thought they heard multiple loud noises. She said people locked themselves in offices until authorities evacuated the complex that houses insurance, medical and law offices.

Becky Neher, who works for a title company in the building, said the two gunshots she heard sounded like two pieces of metal banging against each other.

Watching from her second-story office, she saw people leaving the building.

"Someone yelled, 'We have a shooter,"' she said. She saw two victims lying on the ground outside the back side of the building. She said health care workers who have offices in the complex came out to help.